1. Technical Field
The disclosure generally relates to a semiconductor structure, and, more particularly, to a nitride semiconductor structure.
2. Description of Related Art
In recent years, nitride photodiodes have been broadly used in various fields. In a nitride semiconductor structure, since the silicon substrate bears the merits of high thermal conductivity and low cost, a large dimension nitride semiconductor structure with a silicon substrate as a base is an essential element in a nitride photodiode.
Using a gallium nitride semiconductor layer as an exemplary illustration, the lattice difference between a gallium nitride semiconductor layer and a silicon substrate is about 17%, and the difference in thermal expansion coefficients between the two is about 54%. Aside from creating a rupture on the thin film due to the excessive thermal stress generated during the cooling period, the above differences may also generate internal strain in the gallium nitride semiconductor layer during the epitaxy process, resulting in a cracking of the thin film and a formation of defects. Accordingly, resolving the incompatibilities of lattices and thermal expansion coefficients between a nitride semiconductor layer and a silicon substrate to mitigate the rupture of wafers and to obviate the generation of defects is still an issue for the industry to endeavour.